The long-term goal is to understand surface macromolecular structure and biology of free-swimming cercariae of S. mansoni sufficiently well so as to develop rational means for combating infection. Cercariae bear a conspicuous glycocalyx over essentially their entire surface. This material is immunogenic, but has not been thorough characterized. During invasion of the mammalian host, the glycocalyx is discarded and stored components are mobilized to generate a new surface. Since the glycocalyx is readily accessible prior to infection and since it is likely to be essential for survival of cercariae, this investigation is centered on its biochemical, molecular and immunological characterization. A) Biochemical characterization of the intact glycocalyx: Determination of its heterogeneity, linkage between carbohydrate and the putative protein backbone. Determination of the composition, size, and charge of carbohydrate fragments. Characterization of the size of the putative polypeptide backbone, partial sequence. B) Mechanism of glycocalyx release during transformation: Is release enzyme mediated and if so can the enzymes be identified and purified? Can cercariae survive and infect mice after enzymatic removal of the glycocalyx? Chemical characterization of the shed glycocalyx. Inhibitory potential of antibodies which bind release factors. C) Immunological characterization of the glycocalyx: Which carbohydrate and/or polypeptide components are immunogenic and give protection against parasite challenge? Which are immunosuppressive? Humoral and cell- mediated immune response after immunization. D) Glycocalyx backbone polypeptide cDNA and gene characterization: Obtain cDNA from a cercarial or sporocyst gt11 library, determine its restriction map and sequence. Study tissue distribution of mRNA expression. Detect the corresponding gene. This project relates directly to Project 3 in terms of identification of vaccine candidates and identification of relevant S. mansoni cDNA clones. It depends on Core B for S. mansoni parasites and Core D for ultrastructural analyses of cercariae and schistosomula.